Sema: Fix incorrect 'static' operator check

We were not enforcing that operators were static if
the operator was defined in a final class, or if it
was defined in a non-final class but the operator was
itself final.

Fixes <rdar://problem/31469036>.

Author: slavapestov

lib/Sema/TypeCheckDecl.cpp

@@ -4733,35 +4733,24 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     // Check for static/final/class when we're in a type.
     auto dc = FD->getDeclContext();
     if (dc->isTypeContext()) {
-      // Within a class, operator functions must be 'static' or 'final'.
-      if (auto classDecl = dc->getAsClassOrClassExtensionContext()) {
-        // For a class, we also need the function or class to be 'final'.
-        if (!classDecl->isFinal() && !FD->isFinal() &&
-            FD->getStaticSpelling() != StaticSpellingKind::KeywordStatic) {
-          if (!FD->isStatic()) {
-            TC.diagnose(FD->getLoc(), diag::nonstatic_operator_in_type,
-                        operatorName,
-                        dc->getDeclaredInterfaceType())
-              .fixItInsert(FD->getAttributeInsertionLoc(/*forModifier=*/true),
-                           "static ");
-
-            FD->setStatic();
-          } else {
-            TC.diagnose(FD->getLoc(), diag::nonfinal_operator_in_class,
-                        operatorName, dc->getDeclaredInterfaceType())
-              .fixItInsert(FD->getAttributeInsertionLoc(/*forModifier=*/true),
-                           "final ");
-            FD->getAttrs().add(new (TC.Context) FinalAttr(/*IsImplicit=*/true));
-          }
-        }
-      } else if (!FD->isStatic()) {
-        // Operator functions must be static.
-        TC.diagnose(FD, diag::nonstatic_operator_in_type,
+      if (!FD->isStatic()) {
+        TC.diagnose(FD->getLoc(), diag::nonstatic_operator_in_type,
                     operatorName,
                     dc->getDeclaredInterfaceType())
           .fixItInsert(FD->getAttributeInsertionLoc(/*forModifier=*/true),
                        "static ");
+
         FD->setStatic();
+      } else if (auto classDecl = dc->getAsClassOrClassExtensionContext()) {
+        // For a class, we also need the function or class to be 'final'.
+        if (!classDecl->isFinal() && !FD->isFinal() &&
+            FD->getStaticSpelling() != StaticSpellingKind::KeywordStatic) {
+          TC.diagnose(FD->getLoc(), diag::nonfinal_operator_in_class,
+                      operatorName, dc->getDeclaredInterfaceType())
+            .fixItInsert(FD->getAttributeInsertionLoc(/*forModifier=*/true),
+                         "final ");
+          FD->getAttrs().add(new (TC.Context) FinalAttr(/*IsImplicit=*/true));
+        }
       }
     } else if (!dc->isModuleScopeContext()) {
       TC.diagnose(FD, diag::operator_in_local_scope);

test/decl/func/operator.swift

@@ -228,7 +228,7 @@ class C0 {
 }
 
 class C1 {
-  final func %%%(lhs: C1, rhs: C1) -> C1 { return lhs }
+  final func %%%(lhs: C1, rhs: C1) -> C1 { return lhs } // expected-error{{operator '%%%' declared in type 'C1' must be 'static'}}{{3-3=static }}
 }
 
 final class C2 {